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Hurricane GREG (Text)

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HURRICANE GREG DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072011
800 AM PDT THU AUG 18 2011

SATELLITE IMAGERY SHOWS THAT GREG HAS A WELL-DEFINED CENTRAL DENSE
OVERCAST WITH OCCASIONAL HINTS OF AN EYE APPEARING IN VISIBLE AND
INFRARED IMAGERY.  SATELLITE INTENSITY ESTIMATES ARE NOW 77 KT FROM
SAB AND TAFB...SO THE INITIAL INTENSITY IS INCREASED TO 75 KT.  THE
CIRRUS OUTFLOW IS GOOD OVER THE SOUTHWESTERN SEMICIRCLE AND POOR
ELSEWHERE.

THE INITIAL MOTION IS 285/16.  GREG IS LOCATED BETWEEN A LARGE
MID/UPPER-LEVEL RIDGE OVER THE SOUTHERN UNITED STATES AND
NORTHWESTERN MEXICO AND A LARGE GYRE IN THE INTERTROPICAL
CONVERGENCE ZONE TO ITS SOUTHWEST.  THE DYNAMICAL MODELS FORECAST
THE GYRE TO GRADUALLY WEAKEN DURING THE NEXT 24-48 HR...AND THEY
FORECAST THE WESTERN END OF THE RIDGE TO WEAKEN AFTER 72 HR IN
RESPONSE TO A DEVELOPING DEEP-LAYER TROUGH OVER THE NORTHEASTERN
PACIFIC.  THIS EVOLUTION SHOULD CAUSE GREG TO TURN MORE WESTWARD
DURING THE FIRST 24 HR...WITH A MOTION TOWARD THE WEST AT A
DECREASING FORWARD SPEED THROUGH THE REMAINDER OF THE FORECAST
PERIOD.  WHILE THE TRACK GUIDANCE AGREES WITH THIS SCENARIO...IT
SHOULD BE NOTED THAT THE GFS...ECMWF...AND CANADIAN MODELS ARE
HAVING PROBLEMS FORECASTING THE INTERACTION OF GREG WITH THE GYRE
DUE TO A POOR INITIALIZATION OF THE HURRICANE.  THE NEW FORECAST
TRACK IS AN UPDATE OF THE PREVIOUS FORECAST AND LIES A LITTLE TO
THE NORTH OF THE CENTER OF THE GUIDANCE ENVELOPE.

THERE IS A OPPORTUNITY FOR ADDITIONAL STRENGTHENING TODAY.  AFTER
THAT...THE FORECAST TRACK TAKES GREG OVER COOLER WATERS WHERE STEADY
WEAKENING IS EXPECTED UNTIL GREG DEGENERATES INTO A REMNANT LOW IN
ABOUT 120 HR.  THE NEW FORECAST INTENSITIES...WHICH ARE A BLEND OF
THE SHIPS...LGEM...AND ICON GUIDANCE...ARE SLIGHTLY LOWER THAN THE
PREVIOUS FORECAST THROUGH 72 HR AND THEN ARE THE SAME AS THE
PREVIOUS FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/1500Z 18.5N 111.5W   75 KT  85 MPH
 12H  19/0000Z 18.9N 113.6W   80 KT  90 MPH
 24H  19/1200Z 19.1N 116.0W   80 KT  90 MPH
 36H  20/0000Z 19.2N 118.0W   65 KT  75 MPH
 48H  20/1200Z 19.2N 120.0W   55 KT  65 MPH
 72H  21/1200Z 19.0N 122.5W   40 KT  45 MPH
 96H  22/1200Z 19.0N 124.5W   30 KT  35 MPH
120H  23/1200Z 19.0N 126.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BEVEN
 
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